Center-square.



No. ssmsslr PatentdNov. l9, mm. W. A. DUNBAB.

CENTER SQUARE.

(Application filed June 8, 1901.) (No Model.)

UNTTED STATES PATENT OFFICE.

\VlLLlAM A. DUNBAR, OF LYNN, MASSACHUSETTS.

CENTER-SQUARE.

SPECIFIGATION formingpart of Letters Patent No. 686,891, dated November 19, 1901.

Application filed June 8, 1901. Serial N- 63,8Z7. (No model.)

To aZZ whom it may concern.-

Be it known that I, WILLIAM A. DUNBAR, a citizen of the United States, residing at Lynn, in the county of Essex and State of Massachusetts, have invented certain new and useful Improvements in Center-Squares; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The present invention relates to an improvement in center-squares.

The object of myinvention is to improve the construction of center-squares in order to adapt them to a larger variety of work.

To the above end the present invention 0011- sists in the improved center-square hereinafter described and claimed.

In the accompanying drawings, illustrating the preferred form of my invention, Figure 1 is a front elevation, Fig. 2 a side elevation, and Fig. 3 a rear elevation, of my improved center-square. Fig. 4 is a detail view, and Fig. 5 is a diagrammatic view, hereinafter described.

The head 1 consists of a base 2, provided with arms 3 3, arranged preferably at right angles to each other and at angles of fortyfive degrees to the base. The base is pro-' vided with a V- shaped groove 4 on its front side, arranged at right angles to the bisectrix a of the angle between the arms 3 3. The base is extended in both directions from the center and carries two or more blades 5 5*, provided with bases 6, having projections thereon which fit the groove 4. The blades 5"* and 5 are provided with ruling edges extended parallel to the bisectrix a. The blades 5 and 5 are secured to the base 2 by means of bolts 7, which extend through the slot Sin the base and are provided with beads 9,Which engage the grooves on the rear of the base 2. Thumb-nuts 11 are provided by means of which the blades may be fixed in desired position. The base 2 is provided with a scale 12, which is graduated in opposite directions from the center. The ruling edges of the blades {EL and 5 are beveled at 13 opposite the scale 12, so that the blades may be set with relation to the bisectrix a of the angle of the square. A right-angle blade 14 is provided which is adapted to be secured to either one or the other of the blades 5 5 in order to draw lines at right angles to the bisectrix of the angle of the square or for any other purpose desired. The right-angle blade 14 (illustrated in detail in Fig. 4) has a blade proper and a base 15, which is adapted to rest upon the front side of one of the blades 5 and 5 Aclamp 16 is provided which is pivoted at 17 between the cars 18, secured to the base 15. A cam-lever 19, pivoted at 20 between the same ears, is provided to operate the clamp 16. It is to be noted that the blade 14 lies in the plane of the bladefi. By setting one of the blades at the zero-point on the scale my improved center-square maybe used in the same manner as the ordinary centersquare in laying 0d the center of a piece of shafting or the like. By setting the two blades 5 and 5 atthe distances from the center desired parallel lines may be ruled on the end of a piece of shafting or the like. Heretofore, so far as I am aware, it has never been proposed to provide a center-square with two blades, by means of which parallel lines may be ruled upon the work, and in order to accomplish this result it was necessary to move the blade from one position to another and parallel lines could not be accurately ruled without laying off measurements upon the work. According to my invention I am enabled to rule two parallel lines upon the Workatonesettingofthedevicethereon. Both of these lines may be upon the same side of the center of the work or upon opposite sides of the center, as desired. This is a valuable and important feature of my invention, and it flows directly from providing the centersquare with a base and two parallel blades. The right-angle blade 14 enables me to scribe lines upon the work at right angles to each other. Heretofore, so far as I am aware, no center-square has been provided with means for scribing lines upon the work at right angles to each other without the use of measurements laid olf upon the work. By the use of my improved center-square the dimensions are measured from the center without the necessityof previously determining such center. Thus if it were desired to lay oft upon the end of the cylindrical piece of work the figure (indicated in Fig. 5) consisting of the two parallellines c and cl,distant,respectively,

from the center three-eighths and five-eighths of an inch and the line 6 at right angles to such line distant from the center one-quarter of an inch, one would proceed as follows: Set the blade 5 on the right of the bisectrix at a distance therefrom indicated on the scale by set the blade 5* on the same side fiveeighths of an inch from the center, and draw the two lines o and d, extending the line 0 across the whole width of the Work, as indicated in broken lines. Then set the blade 5 on the right of the bisectrix at a distance of one-fourth of an inch therefrom and push the blade 5 to the left, securing it in position, and put on it the right-angle blade 14:. Then apply the center-square to the Work, bringing the edge of the right-angle blade 14 into coincidence with the line 0 extended. Then scribe the line 6 between the lines o and d. It will be noted that the parallel lines were drawn at one setting of the device upon the work and that the line 6 is drawn at rightangles to these lines, all at their proper distances from the center of the work and without laying any measurements off on the work i or determining the center of the work.

Having thus described my invention, I claim- 1. A center-square, having, in combination, a square provided with a base extended in both directions from, and at right angles to, the bisectrix of the angle ofthe square, two adjustable independent blades provided with ruling edges parallelto each other and to the said bisectrix, said blades and base being provided with cooperating grooves and projections to secure the correct parallelism of the blades to each other and to the said hisectrix, and independent fastening means for securing each blade in adjusted position to the base, substantially as described.

2. A center-square, having, in combination, a square, a base at right angles to the bisectrix of the angle of the square, a blade having its edge parallel with the bisectrix of the angle of the square adjustably mounted on said base and-a right-angle blade adjustably secured to said blade, substantially as described.

In testimony whereof I affix my signature in presence of two witnesses.

WILLIAM A. DUNBAR.

Witnesses:

HORACE VAN EVEREN, ALFRED H. HILDRETH. 

